Re: Traditional Aikido vs Nihon Goshin
Answering a question with a question:
What are your goals? Aikido rank is not all that transferrable in general. I train at three dojo, ranking at only one, and neither of the others formally recognizes my rank--on the other hand, it doesn't make any difference in their willingness to teach me. If I wanted to hold rank with them I would have to re-test, which would take a long time--but I'd still be learning while I did it.
If your goal is to learn some aikido, choose the school whose teaching style and environment resonates with you, the teacher(s) whose aikido you admire and want to imitate.
If you have a more specific goal such as "I want to train at Aikikai Hombu in a few years" then the rank question becomes a lot more important. Or if you want to teach within a specific organization, then you need rank in that organization. It all depends on your goals.